Configuration of control channels in a mobile communication system

ABSTRACT

The invention relates to a method, apparatus and system for configuring control channels in a mobile communication network and a mobile station. In order to suggest another improved scheme for configuring control channels, in particular control channels related to the transmission of user data the invention suggests aligning the size of the control channel information of different formats to an equal number of coded control channel information bits and/or modulation symbols for each control channel. The control channels may comprise scheduling related control information. According to another aspect of the invention, the size of the control channel information is aligned by means of modulation and/or coding, however the control channel information is aligned to one out of a set of numbers of coded control channel information bits and/or modulation symbols for each control channel.

BACKGROUND

1. Technical Field

The invention relates to a method, apparatus and system for configuringcontrol channels in a mobile communication network and a mobile station.

2. Description of the Related Art

Packet-Scheduling and Shared Channel Transmission

In wireless communication systems employing packet-scheduling, at leastpart of the air-interface resources are assigned dynamically todifferent users (mobile stations—MS). Those dynamically allocatedresources are typically mapped to at least one shared data channel(SDCH). A shared data channel may, for example, have one of thefollowing configurations:

-   -   One or multiple codes in a CDMA (Code Division Multiple Access)        system are dynamically shared between multiple MS.    -   One or multiple subcarriers (subbands) in an OFDMA (Orthogonal        Frequency Division Multiple Access) system are dynamically        shared between multiple MS.    -   Combinations of the above in an OFCDMA (Orthogonal Frequency        Code Division Multiplex Access) or a MC-CDMA (Multi Carrier-Code        Division Multiple Access) system are dynamically shared between        multiple MS.

The main benefits of packet-scheduling are the multi-user diversity gainby time domain scheduling (TDS) and dynamic user rate adaptation.

Assuming that the channel conditions of the users change over time dueto fast (and slow) fading, at a given time instant the scheduler canassign available resources (codes in case of CDMA, subcarriers/subbandsin case of OFDMA) to users having good channel conditions in time domainscheduling,

Specifics of DRA and Shared Channel Transmission in OFDMA

Additionally to exploiting multi-user diversity in time domain by TimeDomain Scheduling (TDS), in OFDMA multi-user diversity can also beexploited in frequency domain by Frequency Domain Scheduling (FDS). Thisis because the OFDM signal is in frequency domain constructed out ofmultiple narrowband subcarriers (typically grouped into subbands), whichcan be assigned dynamically to different users. By this, the frequencyselective channel properties due to multi-path propagation can beexploited to schedule users on frequencies (subcarriers/subbands) onwhich they have a good channel quality (multi-user diversity infrequency domain).

As briefly introduced earlier in real systems the OFDM(A) physicalresources (subcarriers in frequency domain and OFDM symbols in timedomain) are defined in terms of subbands in frequency domain and slots,sub-frames, etc. in time domain. For exemplary reasons, in the followingdescription the following definition is used (see also 3GPP TS 36.211V0.2.1, “Physical Channels and Modulation (Release 8),” November 2006,available at http://www.3gpp.org and incorporated herein by reference):

-   -   A slot is defined in time domain and spans over N_(sym)        consecutive OFDM symbols    -   A sub-frame is defined in time domain and spans over N_(slot)        consecutive slots    -   A frame is defined in time domain and spans over N_(sf)        consecutive sub-frames    -   A resource element (RE) defines the resource of one OFDM symbol        in time domain and one subcarrier in frequency domain, which        defines one modulation symbol    -   A subband is defined in frequency domain and spans over N_(sc)        consecutive subcarriers    -   A physical resource block (PRB) spans over one subband and one        slot and contains N_(sym)×N_(sc) resource elements    -   A virtual resource block (VRB) has the same size as a PRB in        terms of resource elements, but has no relation to the mapping        on the physical resources

FIG. 3 shows an exemplary downlink resource grid of an OFDMA channel bymeans of which the structure of the resource blocks will be explained infurther detail. For exemplary purposes, a frame structure as, forexample, proposed in 3GPP TR 25.814, “Physical layer aspects for evolvedUniversal Terrestrial Radio Access (UTRA), (Release 7),” version 7.1.0,September 2006 (available at http://www.3gpp.org and incorporated hereinby reference) or 3GPP TS 36.211 is assumed.

Accordingly a frame may, for example, have a length (in the time domain)of 10 ms consisting of 10 sub-frames of 1.0 ms length. Each sub-framemay be divided in two slots each comprising a given number of N_(symb)^(DL)=7 OFDM symbols in the time domain and spanning the entire downlinkchannel bandwidth available (i.e., all N_(BW) ^(DL) subcarriers intowhich the downlink channel bandwidth is divided). Each of the OFDMsymbols consists of N_(BW) ^(DL) modulation symbols or resourceelements.

As illustrated in FIG. 3, a resource block is formed by a given numberof resource elements or modulation symbols in a frequency range(specified by the bandwidth of N_(RB) subcarriers) and a given number ofOFDM symbols in the time domain (or more precisely the modulationsymbols of the given number of OFDM symbols in a frequency range definedby the bandwidth of N_(RB) subcarriers). Thereby, a resource block mayhave the length of a sub-frame or a slot of the sub-frame in the timedomain. Further, it may be assumed that a given number of resourceelements in a resource block (corresponding to a given number ofmodulation symbols of N_(symb) ^(L)1/L2 OFDM symbols in a resourceblock) are reserved for control signaling while the remaining resourceelements are used for user data.

For the 3GPP Long Term Evolution (see 3GPP TR 25.814), a 10 MHz system(normal cyclic prefix) may consist of 600 subcarriers with a subcarrierspacing of 15 kHz. The 600 subcarriers may then be grouped into 50subbands (12 adjacent subcarriers), each subband occupying a bandwidthof 180 kHz. Assuming that a slot has a duration of 0.5 ms, a resourceblock (RB) spans over 180 kHz and 0.5 ms according to this example.

A number of physical channels and also reference signals will be mappedonto the physical resources (REs, PRBs). In the following, we will focuson the Shared Data CHannel (SDCH) and the L1/L2 control channels, whichcarry layer 1 and layer 2 control information for the data on the SDCH.For simplicity reasons the mapping of other channels and referencesignals is not considered.

Typically, a physical resource block is the smallest physical allocationunit on which the SDCH is mapped. In case virtual resource blocks aredefined, an SDCH might be mapped onto a virtual resource block first anda virtual resource block might then be mapped either on a singlephysical resource block (localized mapping) or might be distributed ontomultiple physical resource blocks (distributed mapping).

In order to exploit multi-user diversity and to achieve scheduling gainin frequency domain, the data for a given user should be allocated onphysical resource blocks on which the users have a good channelcondition (localized mapping).

An example for a localized mapping is shown in FIG. 1, where onesub-frame spans over one slot. In this example neighboring physicalresource blocks are assigned to four mobile stations (MS1 to MS4) in thetime domain and frequency domain.

Alternatively, the users may be allocated in a distributed mode (DM) asshown in FIG. 2. In this configuration a user (mobile station) isallocated on multiple resource blocks, which are distributed over arange of resource blocks. In distributed mode a number of differentimplementation options are possible. In the example shown in FIG. 2, apair of users (MSs1/2 and MSs 3/4) share the same resource blocks.Several further possible exemplary implementation options may be foundin 3GPP RAN WG#1 Tdoc R1-062089, “Comparison between RB-level andSub-carrier-level Distributed Transmission for Shared Data Channel inE-UTRA Downlink,” August 2006 (available at http://www.3gpp.org andincorporated herein by reference).

It should be noted that multiplexing of localized mode and distributedmode within a sub-frame is possible, where the amount of resources (RBs)allocated to localized mode and distributed mode may be fixed,semi-static (constant for tens/hundreds of sub-frames) or even dynamic(different from sub-frame to sub-frame).

In localized mode as well as in distributed mode in—a givensub-frame—one or multiple data blocks (which are, inter alia, referredto as transport-blocks) may be allocated separately to the same user(mobile station) on different resource blocks, which may or may notbelong to the same service or Automatic Repeat reQuest (ARQ) process.Logically, this can be understood as allocating different users.

Link Adaptation

In mobile communication systems link adaptation is a typical measure toexploit the benefits resulting from dynamic resource allocation. Onelink adaptation technique is AMC (Adaptive Modulation and Coding). Here,the data-rate per data block or per scheduled user is adapteddynamically to the instantaneous channel quality of the respectiveallocated resource by dynamically changing the modulation and codingscheme (MCS) in response to the channel conditions. This may require achannel quality estimate at the transmitter for the link to therespective receiver. Typically hybrid ARQ (HARQ) techniques are employedin addition. In some configurations it may also make sense to usefast/slow power control.

L1/L2 Control Signaling

In order to inform the scheduled users about their resource allocationstatus, transport format and other user data related information (e.g.,HARQ), Layer 1/Layer 2 (L1/L2) control signaling is transmitted on thedownlink (e.g., together with the user data). Thereby, each user (or agroup of users identified by a group ID) may be considered to beassigned a single L1/L2 control channel for providing L1/L2 controlinformation to the respective user(s).

Generally, the information sent on the L1/L2 control signaling may beseparated into the following two categories. Shared Control Information(SCI) carrying Cat. 1 information and Dedicated Control Information(DCI) carrying Cat. 2/3. The format of these types of control channelinformation has been, for example, specified for downlink user datatransmissions in 3GPP TR 25.814:

TABLE 1 Field Size Comment Cat. 1 ID (UE or group specific) [8-9]Indicates the UE (or group of (Resource UEs) for which the dataindication) transmission is intended Resource assignment FFS Indicateswhich (virtual) resource units (and layers in case of multi- layertransmission) the UE(s) shall demodulate. Duration of assignment 2-3 Theduration for which the assignment is valid, could also be used tocontrol the TTI or persistent scheduling. Cat. 2 Multi-antenna relatedinformation FFS Content depends on the (transport MIMO/beamformingschemes format) selected. Modulation scheme 2 QPSK, 16QAM, 64QAM. Incase of multi-layer transmission, multiple instances may be required.Payload size 6 Interpretation could depend on, e.g., modulation schemeand the number of assigned resource units (c.f. HSDPA). In case ofmulti- layer transmission, multiple instances may be required. Cat. 3 Ifasynchronous Hybrid ARQ 3 Indicates the hybrid ARQ process (HARD)process number the current transmission is addressing. Redundancy 2 Tosupport incremental version redundancy. New data 1 To handle soft bufferclearing. indicator If synchronous Retransmission 2 Used to deriveredundancy hybrid ARQ is sequence version (to support incrementaladopted number redundancy) and ‘new data indicator’ (to handle softbuffer clearing).

Similar, 3GPP TR 25.814 also suggests a L1/L2 control signaling formatfor uplink user data transmission:

TABLE 2 Field Size Comment Resource ID (UE or [8-9] Indicates the UE (orgroup of UEs) assignment group for which the grant is specific)intended. Resource FFS Indicates which uplink resources, assignmentlocalized or distributed, the UE is allowed to use for uplink datatransmission. Duration of 2-3 The duration for which the assignmentassignment is valid. The use for other purposes, e.g., to controlpersistent scheduling, ‘per process’ operation, or TTI length, is FFS.Transport Transmission FFS The uplink transmission parameters Format(TF) parameters (modulation scheme, payload size, MIMO-relatedinformation, etc.) the UE shall use. If the UE is allowed to select(part of) the transport format, this field sets (determines) an upperlimit of the transport format the UE may select.

As can be recognized from Table 1 and Table 2 above, the number ofcontrol information bits is variable depending, for example, on thecontrol channel information's relation to uplink or downlink user datatransmissions.

Furthermore, some fields of the control channel information formats mayalso depend on the MIMO transmission mode of the data. For example, ifdata is transmitted in a special MIMO (Multiple Input Multiple Output)mode, the L1/L2 control information for this data may comprisemulti-antenna related information, while this information may be omittedfor data transmission without MIMO. But also for different MIMO schemes(such as Single User (SU) MIMO or Multi User (MU) MIMO) andconfigurations (e.g., rank, number of streams) the control channelinformation (prior to coding) may be different (also with respect to thenumber of bits).

For example, data on an allocated PRB might be transmitted to a UE usingmultiple codewords. In this case HARQ related information, payload sizeand/or modulation scheme might need to be signaled multiple times.Further, MIMO related information may include precoding relatedinformation, where the amount of required precoding information dependson the application of single user MIMO or multi user MIMO, on the rankand/or on the number of streams.

Similarly, the format (and size) of the L1/L2 control information mayalso depend on whether the control channel information relates totransmission of the data in a distributed or localized OFDMtransmission.

In conventional systems (such as, for example, in UMTS High Speed DataPacket Access—HSDPA) the scheduling related control information aretypically transmitted using a fixed modulation and coding scheme (MCS)level, which is known to all mobile stations within a radio cell.

Using a fixed modulation and coding scheme for L1/L2 control signalingwould result in different amounts of resources that would have to beused for the L1/L2 control signaling on the physical channel resourceswhich is however undesirable in view of UE complexity, schedulingflexibility, etc.

BRIEF SUMMARY

One solution to mitigate this problem may be to provide the mobilestations with a map indicating the downlink L1/L2 control channelsresource utilization each sub-frame (for example, in form of so-calledCat. 0 control information). However, this approach may not bedesirable, as it may require additional mobile station complexity, maylead to an additional delay in processing the control channelinformation in the mobile stations and would also require additionaloverhead due to sending the map indicating the downlink L1/L2-controlchannels resource utilization.

Another solution may be to only allow the allocation of predefinedcombination of mobile station (e.g., with predefined MIMOmode/configuration). However, this approach may imply an unacceptablerestriction in scheduling functionality and a significant loss in systemthroughput.

An even further solution may be to send no map indicating the downlinkL1/L2-control channels resource utilization each sub-frame (i.e., noCat. 0 information) and to have no predefinition. This approach wouldthus require the mobile stations to blindly try to decode all possiblecombinations of modulation and coding schemes and mappings on resourceelements to read the different control channels in a sub-frame.Accordingly, this approach would imply a significant and potentiallyundesirable increase in the mobile stations complexity.

A main object of the invention is to suggest another improved scheme forconfiguring control channels, in particular control channels related tothe transmission of user data.

The main object is solved by the subject matter of the independentclaims. Advantageous embodiments of the invention are subject matters ofthe dependent claims.

One main aspect of the invention is thus to align the size of thecontrol channel information of different formats to an equal number ofcoded control channel information bits and/or modulation symbols foreach control channel. The control channels may, for example, comprisescheduling related control information, such as, for example, L1/L2control information. According to a further aspect of the invention, amore flexible solution is proposed that may allow for taking differentgeometries of mobile stations within a cell into account. Similar to theaspect above, the size of the control channel information is aligned bymeans of modulation and/or coding. However, in this exemplary aspect ofthe invention, the control channel information is aligned to one out ofa set of numbers of coded control channel information bits and/ormodulation symbols for each control channel.

A further aspect of the invention is to align the size of the controlchannel information of different formats to an equal number of codedcontrol channel information bits and/or control channel elements foreach control channel. Thereby, a control channel element (CCE)corresponds to a given number of modulation symbols or resourceelements. Thus, the terms “given number of CCEs” and “given number ofmodulations symbols or resource elements” are essentially equivalentfrom a technical point of view, as a single CCE consists in turn of agiven number of modulations symbols or resource elements.

Accordingly, if the application is mentioning the alignment of the sizeof the control channel information of different formats to an equalnumber of coded control channel information bits and/or modulationsymbols for each control channel, this teaching equally applies to thealignment of the size of the control channel information of differentformats to an equal number of control channel elements for each controlchannel.

One embodiment of the invention relates to a method that may be used forfacilitating blind detection of plural control channels in acommunication system on the receiver side. It is assumed that there areplural control channels provided and that the control channelinformation on the control channels have different formats, e.g., arestructured differently and/or may also have different length. Accordingto this embodiment, a transmitting entity of the communication systemmay apply to each control channel a modulation and coding schemeassociated to the format of the control channel information of thecontrol channel. Applying the modulation and coding scheme to thecontrol channel causes a respective generation of an equal number ofcoded control channel information bits (e.g., output by a coder prior tomodulation) and/or modulation symbols (e.g., output by a modulator) foreach control channel.

Whether an equal number of coded control channel information bits andmodulation symbols for each control channel is generated or whether anequal number of modulation symbols for each control channel is generatedmay, for example, depend on the processing of the control channelinformation and/or the configuration of the individual entities (such ascoders, modulators, multiplexers, etc.)

In another embodiment of the invention, the different formats of thecontrol channel information on the control channels have differentnumbers of control channel information bits. In the extreme case, thedifferent control channels' formats all have a different number ofcontrol channel information bits.

In one embodiment, applying a modulation and coding scheme comprisescoding the control channel information at the coding rate yielded by themodulation and coding scheme associated to the control channel's formatand modulating the coded control channels according to the modulationscheme yielded by the modulation and coding scheme associated to arespective control channel's format. Further, the step of applying amodulation and coding scheme may comprise mapping the coded controlchannel information bits or the modulation symbols of the controlchannels to the downlink physical channel resource for transmission. Inone example, the modulation symbols may be subjected to OFDM modulationand are subsequently mapped to the physical channel for transmission.

In one possible and exemplary realization of a modulation and codingschemes for use with the invention, the modulation and coding schemesassociated to the control channels' formats all yield the samemodulation scheme but different coding rates. In this exemplaryrealization, the coder may thus adapt the coding rate so that an equalnumber of coded control channel information bits and—due to the samemodulation scheme in all modulation and coding schemes—also an equalnumber of modulation symbols for each control channel is generated bythe modulator.

The control channel information may have different structures/formats.The control channel information format may, for example, depend on atleast one of the following parameters:

-   -   the control channel's relation to a MIMO scheme or beamforming        scheme utilized or to be utilized for the transmission of user        data,    -   the control channel's relation to uplink or downlink        transmission of user data,    -   the control channel's relation to a utilization of localized        mode or distributed mode OFDM transmission for the transmission        of user data.

Alternatively or in addition thereto, the control channel may carrypaging related information or information related to a response to anuplink (random) access procedure.

In one exemplary embodiment, at least one receiver (of the controlchannels) is preconfigured with a specific MIMO scheme and the receivermay detect in a blind detection fashion whether localized mode ordistributed mode OFDM transmission for the transmission of user data andwhether the control channel relates to uplink or downlink user datatransmission to select the correct modulation and coding scheme fordemodulation and decoding of the control channel. Hence, in thisembodiment, the detection of the transmission mode and the controlchannel information's relation to uplink or downlink, the receiver maydetermine the correct format of the control channel by means of blinddetection and may decode the control channel information from thecontrol channels (please note that not all control channels may need tobe processed by the receiver—see below).

Alternatively, in another embodiment, at least one receiver ispreconfigured for either localized mode or distributed modetransmission. In this case the receiver may use blind detectionmechanisms to detect whether the control channel relates to uplink ordownlink user data transmission and which MIMO scheme or beamformingscheme is used for the transmission of user data transmission to selectthe correct modulation and coding scheme for demodulation and decodingof the control channel.

In some embodiments of the invention, the control channels conveyinformation related to the transmission of user data. For example, thisinformation may be scheduling related control information, such as L1/L2control information. Accordingly, the control channel may also bereferred to as scheduling related control channels or L1/L2 controlchannels in this example.

In one further embodiment, a control channel conveys a resourceindication of the user data, a transport format indication of the userdata, and optionally information related to a retransmission protocolused for transmitting the user data. Alternatively or in addition, acontrol channel may also convey a resource assignment for the user dataand uplink transmission parameters for the user data, and optionallyinformation related to a retransmission protocol used for transmittingthe user data.

According to another embodiment, the control channels may convey controlchannel information related to downlink transmission only, controlchannel information related to uplink transmission only or controlchannel information related to downlink and uplink transmission.

The control channel information of a control channel may conveydifferent types of information. For example, in case the controlchannels convey L1/L2 control information such as Cat. 1, Cat. 2 andoptionally Cat. 3 information, the different information conveyed by acontrol channel may be jointly encoded.

In a further embodiment, the transmitting entity may further transmitthe control channels on a downlink physical channel resource. Asindicated above, a receiving entity may perform a blind detection of atleast a subset of the physical resources on which the control channelsare mapped (e.g., on those physical resources on which a subset ofcertain control channel information formats is conveyed). Thereby, thereceiving entity's knowledge on the modulation and coding schemesassociated to the different formats of the control channel informationon the control channels is used to limit the number of trials in theblind detection.

Further, according to one exemplary embodiment, the number of controlchannel information bits (or a control channel information format) of acontrol channel may be associated to one modulation and coding schemeaccording to a pre-configuration or according to a configurationmessage.

In an exemplary variation of this embodiment, the pre-configuration isachieved by transmitting a higher layer message on the data channel toone or more receiving entities on a dedicated or shared channel. Thismessage may instruct a respective receiving entity to perform a blinddetection on only a subset of the physical resources on which thecontrol channels are mapped and/or a subset of control channelinformation formats.

In an alternative variation of the embodiment, the configuration messagemay, for example, be a broadcast message sent on the broadcast channelto instruct one or more receiving entities to perform a blind detectionon only a subset of the physical resources on which the control channelsare mapped and/or a subset of control channel information formats.

For example, the configuration message may be sent as a separate pieceof control information on a separate control channel. In one exemplaryimplementation, the configuration message and the control channels aretransmitted every sub-frame or slot.

In another embodiment of the invention, one or more receiving entitiesmay be instructed to perform a blind detection on only a subset of thephysical resources on which the control channels are mapped and/orcontrol channel information formats by means of pre-configuration and/ora configuration message.

Further, in another embodiment, a receiving entity may be configured toblindly detect only a subset of the physical resources on which thecontrol channels are mapped and/or a subset of the control channelinformation formats.

As indicated above, another aspect of the invention is to suggest a moreflexible configuration of control channels without thereby, for example,unduly increasing the required mobile station complexity, reducingscheduling flexibility, or the like. Accordingly, in another embodiment,each of the control channels' formats is associated to a number of Nmodulation and coding schemes, where N>1. In this embodiment, allmodulation and coding schemes, when applied to the control channels ofthe associated formats, may respectively generate a given number out ofN different numbers of coded control channel information bits and/ormodulation symbols. In one exemplary embodiment, the output sizes areinteger multiples of the smallest output size in order to simplifymultiplexing of the control channels.

Accordingly, when applying a modulation and coding scheme to the controlchannels, one out of the N modulation and coding schemes associated to aformat of a control channel may be selected. This selection may, forexample, be based on the geometry of the receiver in the radio cell orother parameters such as received signal strength, fading or frequencyselectivity of the channel, the receiver type or the available transmitpower. The selected modulation and coding scheme may be applied to thecontrol channel information of the control channel.

Another embodiment of the invention considers the mapping of the controlchannels to different aggregation sizes—that is, to different numbers ofmodulation symbols or control channel elements. The control channelinformation bits of a respective control channel format are mapped to atleast one out of a set of aggregation sizes, wherein each of theaggregation sizes is given by a number of modulation symbols or controlchannel elements.

Accordingly, further restrictions may be considered in this mapping. Forexample, the control channel information bits of a respective controlchannel format may be mapped only to those aggregation sizes that yielda code rate for the control channel information bits achieving a givenreliability criterion, such as a desired maximum block error rate. Inaddition or as another example, the control channel information bits ofa respective control channel format may also be mapped only to thoseaggregation sizes that yield a code rate for the control channelinformation bits above a minimum code rate or below a maximum code rate.In another example, the aggregation sizes are mutually distinct.

A further exemplary embodiment considers the systems where differentbandwidths may be used for transmission. In these systems, it may beadvantageous, if the control channel information bits of at least onecontrol channel format are always mapped to the same aggregation size oraggregation sizes, irrespective of the system bandwidth.

In a further embodiment of the invention, a subset of the controlchannels for conveying control information related to uplink user datatransmission and a subset of the control channels for conveying controlinformation related to downlink user data transmission may beconfigured. This may have the advantage that, for example, receivingentities that only listen to downlink services may only need to processthose control channels that relate to user data transmissions on thedownlink. Similarly, according to another embodiment, a subset of thecontrol channels for conveying control information for user datatransmission with MIMO or in a specific MIMO mode may be configured.

In another embodiment of the invention, the control channel informationof a control channel comprises a format identifier, which may yield thecontrol channel information format of the respective control channel.

In an alternative embodiment, the control channel information of acontrol channel comprises a format identifier, which may yield thecontrol channel information format of the respective control channel, iffor a given control channel information bits size multiple formatsexist.

Further, it may be advantageous, if a higher level modulation and codingscheme (or higher code rate only) is used for control channels conveyingcontrol channel information comprising MIMO information than for controlchannels conveying control channel information comprising no MIMOcontrol information.

Further, it may be advantageous, if a higher level modulation and codingscheme (or higher code rate only) is used for control channels conveyingcontrol channel information comprising more MIMO information than forcontrol channels conveying control channel information comprising lessMIMO control information.

Another embodiment of the invention is related to a base station forconfiguring plural control channels in a mobile communication system.The base station may comprise a transmitting entity for applying to eachcontrol channel a modulation and coding scheme associated to the formatof the control channel information of the control channel, therebyrespectively generating an equal number of coded control channelinformation bits and/or modulation symbols for each control channel.

In some embodiments of the invention, the base station further comprisesa coder for coding the control information at the coding rate yielded bythe modulation and coding scheme associated to the control channel'sformat, a modulator for modulating the coded control channels accordingto the modulation scheme yielded by the modulation and coding schemeassociated to a respective control channel's format and a mapping unitfor mapping the coded control channel information bits or the modulationsymbols of the control channels to the downlink physical channelresource for transmission.

In a variation of the embodiment, the base station also includes amultiplexer for multiplexing the coded control channel information bitsof different control channels prior to their modulation by themodulator. Alternatively, the multiplexer could multiplex controlchannel information bits of different control channels prior to theircoding by the coder.

A further embodiment is related to a base station that is adapted toperform or to participate in the steps of the method for facilitatingthe blind detection of control channels according to one of thedifferent embodiments and variations thereof described herein.

Another embodiment relates to a mobile station for use in a mobilecommunication system. The mobile station may, for example, comprise areceiver for receiving at least a subset of a plurality of controlchannels from a downlink physical channel resource, wherein the controlchannels have different formats. A modulation and coding schemeassociated to the format of a respective control channel has beenapplied to the respective control channel by a transmitting entity.Moreover the mobile station may include a processing unit for performinga blind detection of the subset of control channels to reconstruct thecontrol channel information of a respective received control channel,wherein the modulation and coding schemes associated to the differentformats of the control channel information on the control channels areused to limit the number of trials in the blind detection.

In a further embodiment, the mobile station utilizes the following meansof the mobile station to perform the blind detection. A demultiplexingunit (demultiplexer) may be used for demultiplexing the received signalof the respective received control channels to modulation symbols.Further, the mobile station may comprise a demodulator for demodulatingthe modulation symbols to soft decision values and constructing acodeword consisting of a given number of coded control channelinformation bits, and a decoder for decoding the coded control channelinformation bits (also referred to as a codeword) to obtain the controlchannel information bits. Thereby, at least one of the demultiplexingunit, the demodulator and the decoder uses the mobile station'sknowledge on the modulation and coding schemes associated to thedifferent formats of the control channel information on the controlchannels is used to limit the number of trials in the blind detection.

The mobile station according to another exemplary embodiment of theinvention is adapted to perform or to participate in the steps of themethod for facilitating blind detection of control channel according toone of the various embodiments and variations thereof described herein.

Another embodiment of the invention relates to a mobile communicationsystem for transmitting plural control channels having differentformats. This system may comprise a transmitting entity (e.g., a basestation as described herein) for applying to each control channel amodulation and coding scheme associated to the format of the controlchannel information of the control channel, thereby respectivelygenerating an equal number of coded control channel information bitsand/or modulation symbols for each control channel and at least onereceiving entity (e.g., a mobile station as described herein) to receiveat least a subset of the control channels.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the following the invention is described in more detail in referenceto the attached figures and drawings. Similar or corresponding detailsin the figures are marked with the same reference numerals.

FIG. 1 shows an exemplary data transmission to users in an OFDMA systemin localized mode (LM) having a distributed mapping of L1/L2 controlsignaling,

FIG. 2 shows an exemplary data transmission to users in an OFDMA systemin distributed mode (DM) having a distributed mapping of L1/L2 controlsignaling,

FIG. 3 shows an exemplary resource grid of a slot of an OFDM channelstructure according to 3GPP TS 36.211,

FIG. 4 shows an exemplary resource grid of a sub-frame of an OFDMchannel according to an embodiment of the invention,

FIG. 5 shows an illustrative example of a control channel configurationusing a single modulation and coding scheme for all control channels ina resource grid as shown in FIG. 4,

FIGS. 6 and 7 show illustrative examples of control channelconfigurations in a resource grid as shown in FIG. 4 according todifferent exemplary embodiments of the invention,

FIGS. 8 and 9 show two exemplary structures of the processing of controlchannel information of plural control channels on the Physical Layeraccording to different embodiments of the invention,

FIG. 10 shows, in accordance with an exemplary embodiment of theinvention, the use of two different modulation and coding schemes havinga common modulation scheme for aligning the number of coded controlinformation bits of the control channel information of control channels,where the control channel information have different formats,

FIG. 11 shows, in accordance with an exemplary embodiment of theinvention, the use of two different modulation and coding schemes foraligning the number of modulation symbols of the control channelinformation of control channels, where the control channel informationhave different formats,

FIG. 12 shows, in accordance with an exemplary embodiment of theinvention, the use of different modulation and coding schemes foraligning the number of modulation symbols of the control channelinformation of control channels to two numbers of modulation symbols,where the control channel information have different formats,

FIG. 13 shows, in accordance with an exemplary embodiment of theinvention, the use of different modulation and coding schemes foraligning the number of modulation symbols of the control channelinformation of a control channel to two numbers of modulation symbols,where the control channel information have different formats, forexample based on channel quality information,

FIG. 14 shows several different formats of control channel informationand their mapping to a single codeblock size by means of modulation andcoding according to an exemplary embodiment of the invention,

FIG. 15 shows several different formats of control channel informationand their mapping to two different codeblock sizes by means ofmodulation and coding according to an exemplary embodiment of theinvention,

FIG. 16 shows a mobile communication system according to one embodimentof the invention in which the ideas of the invention may be implemented,

FIG. 17 illustrates another exemplary embodiment of the invention wherecontrol channel information formats are mapped to different numbers ofcoded control channel information and/or modulation symbols depending onthe format size, and

FIG. 18 illustrates another exemplary embodiment of the invention wherecontrol channel information formats are mapped to different numbers ofcoded control channel information and/or modulation symbols depending onthe format size and optionally another parameter, such as, e.g., thechannel quality, and

FIG. 19 shows two exemplary resource grids of a sub-frame of an OFDMchannel according to different embodiments of the invention, wherein inthe left resource grid the control channel are mapped in distributedmode and wherein in the right resource grid the control channel aremapped in localized mode to the OFDM channel resources.

DETAILED DESCRIPTION

The following paragraphs will describe various embodiments of theinvention. For exemplary purposes only, most of the embodiments areoutlined in relation to an (evolved) UMTS communication system accordingto the SAE/LTE discussed in the Technical Background section above. Itshould be noted that the invention may be advantageously used, forexample, in connection with a mobile communication system such as theSAE/LTE communication system previously described, but the invention isnot limited to its use in this particular exemplary communicationnetwork.

The following description will be mainly based on a downlink channelstructure as explained in the Technical Background section. Further, tothe explanations in the technical background section, it may be assumedfor exemplary purposes that two (or more) slots form a sub-frame, whilea given number of sub-frames in turn form a frame on the channel. FIG. 4shows an exemplary resource grid of a sub-frame of an OFDM channelaccording to an embodiment of the invention and is used to illustratethe sub-frame structure assumed for exemplary purposes in most of theembodiments described herein. As can be recognized from FIG. 4, twoslots are supposed to form a sub-frame in the time domain. Hence, asub-frame on an OFDM downlink channel may be assumed to consist of tworesource blocks in a time domain; each resource block being formed by agiven number of N_(RB) ^(DL) subcarriers or a subband in the frequencydomain and a given number N_(symb) ^(DL) of OFDM symbols in the timedomain. Moreover, a given number of OFDM symbols or resourceelements/modulation symbols on a sub-frame may be reserved for controlsignaling (e.g., scheduling related control signaling for user data inthe user data section of the sub-frame). In the embodiment shown in FIG.4 it is assumed for exemplary purposes that the control channels areprovided in the first three OFDM symbols of the sub-frame (i.e., in thisexample the three first OFDM symbols of the first slot of thesub-frame). However, it should be noted that also other mappings of thecontrol signals to the physical resources in a sub-frame may be used.

As has been outlined in the Technical Background section, using a fixedmodulation and coding scheme for the L1/L2 control channels may bedisadvantageous, as the control channel information would be mapped todifferent numbers of modulation symbols and thus utilize differentnumbers of physical radio resources for transmission depending on thecontrol channel information size. This scenario is exemplarily depictedin FIG. 5 (please note that the different patterns of the resourceelements in the control channel related OFDM symbols is intended toillustrate the control channels for different users). In FIG. 5 it isassumed for exemplary purposes that the first three OFDM symbols of theresource block are reserved for the control channels of the users.Hence, depending on the size of the respective control channelinformation format, the number of physical resources (modulationsymbols) for the respective control channels is variable. This has thedisadvantage that for blind detection for receiving the control channelson the mobile station's side, a high complexity receiver in the mobilestations may be required. This is caused by the fact that the possiblelocations of the control channels to be decoded depend on the controlchannel formats. Therefore, in a given sub-frame, a receiver would needto blindly decode all possible combinations and locations of the controlchannel formats.

One main aspect of the invention is to align the size of the controlchannel information of different formats to an equal number of codedcontrol channel information bits, modulation symbols and/or ControlChannel Elements (CCE) for each control channel (a CCE corresponds to agiven number of modulation symbols which may alternatively referred toas resource elements). Thereby, the number of blind detection tries ofthe control channels may be reduced as the location of the controlchannels on the physical resources may be known by the mobile stations(or there is at least a limited number of possible locations).

The alignment of the control channel information according to differentformats may, for example, be achieved by using different modulation andcoding schemes for the different control channels depending on theformat of the control channel information on a respective channel. If,for example, the modulation scheme for all control channels is the same,this may mean that the coding rate of a coder may be configured so as tooutput the same number of coded control channel information bits foreach control channel, so that the control channel information of eachcontrol channel would also be mapped to an equal number of modulationsymbols. If the modulation scheme is variable for the control channels,the coding rate and modulation scheme may be chosen for a respectiveformat of the control channel information, such that the control channelinformation of all control channels gets mapped to the same number ofmodulation symbols or CCEs.

FIG. 6 shows an example of one possible control channel configuration ina resource grid as shown in FIG. 4 according to an exemplary embodimentof the invention. As in FIG. 5, the different patterns of the resourceelements in the control channel related OFDM symbols illustrates thecontrol channels of different users. In contrast to FIG. 5, the use ofdifferent modulation and coding schemes for the control channels of thedifferent users according to the format of the control channelinformation on the respective channels allows alignment of the physicalresource utilization of the different control channels, i.e., allcontrol channels are mapped to a single number of resourceelements/modulation symbols (6 resource elements/modulation symbols/CCEsin the example of FIG. 6).

This may facilitate blind detection of the control channels on thereceiver side, as the relative position of the channels in a frame isknown at the receivers so that—at maximum—the number of availablemodulation and coding schemes for the different control channelinformation formats has to be tested to find the matching modulation andcoding scheme and to decode the respective control channel. As will beexplained further below, the number of tries in blind detection may befurther reduced, e.g., by further (pre)configuration of the receivers.With an implementation according to this aspect of the invention,flexibility in the use of different modulation and coding schemes forcontrol signaling may be possible, while at the same time the number oftries in blind detection of the control channels may be limited to anumber equal to or smaller than the number of different control channelinformation formats. This is in contrast to the potentially much highernumber of tries when needing to blindly detect the location of thecontrol channels on the physical resources.

According to a further aspect of the invention, a more flexible solutionis proposed that may allow for taking different geometries of mobilestations within a cell into account. Apparently, the coding rate for thecontrol channel depends on the number of control channel informationbits to a given number of modulation symbols/resource elements and theutilized modulation scheme. Accordingly, the coding rate increases asthe number of control channel information bits increase, if themodulation scheme and the number of modulation symbols/resource elementsare unchanged. This in turn may yield coding rates for some controlchannels that are not feasible in terms of their performance, e.g., fortransmitting the control channel with a given block error rate (BLER) tomobile stations located at the cell edge experiencing high interferenceand/or low received signal strength (low geometry mobile stations).

Similar to the aspect above, the size of the control channel informationis aligned by means of modulation and/or coding. However, in thisexemplary aspect of the invention, the control channel information isaligned to one out of a set of numbers of coded control channelinformation bits, modulation symbols and/or CCEs for each controlchannel. In some exemplary embodiments, the output sizes are integermultiples of the smallest output size which may, for example, allowsimplifying multiplexing of the control channels.

Hence, for example, again considering the case of having a fixedmodulation scheme for all control channels, the coder may output eithera number of N₁ or N₂ coded control channel information bits for allformats of control channel information conveyed by the control channels,which in turn will be modulated to M₁ or M₂ modulation symbols.Alternatively, if the modulation scheme is also variable, the codercould choose a coding rate so that N coded channel information bits areoutput to the modulator for each control channel, while the modulatormay use different modulation schemes (e.g., depending on the mobilestations geometries) so as to modulate the N coded channel informationbits to M₁ or M₂ modulation symbols. Hence, in one exemplary embodimentof the invention, the different numbers of the coded bits, modulationsymbols and/or CCEs of a control channel information format aremultiples of the smallest of the coded control channel information,modulation symbols and/or CCEs (e.g., M₂=n×M₁, with n being a positiveinteger number), which may be advantageous as it allows for asimplification of the multiplexing of the control channels.

Optionally, there may be additional restrictions to be considered inthis aspect of the invention. E.g., the output sizes M₁ or M₂ of themodulation symbols (also referred to as aggregation sizes herein) may berequired to correspond to 2^(n) times the smallest output size (where nis an integer number, e.g., nε{1,2,4} or nε{1,2,3}). The size of a CCEmay be defined such that the smallest output size of a control channelis identical to a single CCE, which would correspond to n=0 in theexample above.

FIG. 7 shows an example of one possible control channel configuration ina resource grid as shown in FIG. 4 according to an exemplary embodimentof the invention and is used to illustrate this further aspect of theinvention. As in FIG. 5 and FIG. 6, the different patterns of theresource elements in the control channel related OFDM symbols illustratethe control channels of different users. Instead of mapping the controlchannel information of the different formats to a single number of codedcontrol channel information and/or modulation symbols as in FIG. 6,there may be at least two different numbers of coded control channelinformation and/or modulation symbols defined. Accordingly, each controlchannel information format may be associated to a modulation and codingscheme that maps the control channel information of a format to eitherthe first or the second number of coded control channel information,modulation symbols and/or CCEs. Alternatively or in addition, at leastsome of the formats may be associated to two modulation and codingschemes so as to map the control channel information of a format toeither the first or the second number of coded control channelinformation and/or modulation symbols. In FIG. 7 it may be assumed forexemplary purposes that the control channel information is either mappedto three resource elements/modulation symbols or six resourceelements/modulation symbols depending on various reasons. Those reasonsmight be the geometries, the received signal strength, the frequencyand/or time selectivity of the channel of a mobile station (UE) to whichthe control information is dedicated.

Similarly to the embodiments of the invention discussed with respect toFIG. 6, this configuration of the control channels may still allow for asimple blind detection at the receivers. Though the complexity isslightly increased due to having different numbers of coded controlchannel information and/or modulation symbols to which the controlchannel information may be mapped, still the number of tries iscomparably low in comparison to testing all possible locations of thecontrol channels on the physical resources if using a single knownmodulation and coding scheme for all control channels, since the numberof different control channel information formats is expected to belarger than the number of defined control channel sizes (in modulationsymbols).

It should be noted that the control channel locations in FIGS. 5, 6 and7 show a logical representation of the control channel to modulationsymbol, resource element or CCE mapping in order to visualize the sizes.The actual mapping of a given control channel may be distributed in timeand/or frequency domain, e.g., on modulation symbol, resource element orCCE level.

The number of coded control channel information bits, modulation symbolsand/or the CCEs to which a respective control channel carrying controlinformation of a certain format is mapped by means of modulation andcoding may, for example, depend on one or more different parameters.

For example, formats having a size of more than a certain thresholdnumber of control information bits may be mapped to a higher number ofcoded control channel information, modulation symbols and/or CCEs thanformats having a size of less or equal to the threshold number ofcontrol information bits. This may be advantageous in cases the size ofthe control information formats vary significantly, as it may allow forensuring certain reliability in the control signaling and/or maintainingan acceptable level of spectral efficiency. An exemplary embodiment isillustrated in FIG. 17.

In addition or alternatively, another criterion for deciding on which ofthe available numbers of coded control channel information, modulationsymbols and/or CCEs the control channel information of a control channel(i.e., user or group of users respectively) is to be mapped may alsodepend on the geometries of the user(s). For example, in case thechannel quality of a user (e.g., measured in terms of Signal-to-NoiseRatio (SNR), Signal-to-Interference Ratio (SIR), Signal toInterference-plus-Noise Ratio (SINR), etc.) is low (e.g., below athreshold) and the size of the control channel format for that userbeing large in comparison to the other formats, a modulation and codingscheme with high spectral efficiency is likely to be associated to thecontrol channel information format so as to map the control channel to agiven number of coded control channel information and/or modulationsymbols. However, in view of the user's geometry in the cell, thismodulation and coding scheme may not allow to provide the desiredbit-error-rate for the control channel information. This alternative oradditional criterion and the resulting mapping of the control channelinformation of the different formats to different codeblock sizes isexemplarily illustrated in FIG. 18.

The two tables (Tables 3 and 4) below give examples for differentcontrol channel information sizes and the resulting code rates, assumingfor exemplary purposes that the control channels are transmitted withQPSK modulation. In the examples, it is further assumed for exemplarypurposes that the coded control channel sizes (aggregation sizes) givenin modulation symbols (resource elements (REs)) or CCEs are 8, 4 or 2times the smallest size (rightmost column, 1 CCE). Table 3 assumes thata CCE consists of 36 REs, i.e., the smallest coded control channel sizes(CCE aggregation size) is 36 REs or 1 CCE. In Table 4 it is assumes thata CCE consists of 24 REs, i.e., the smallest coded control channel sizes(CCE aggregation size) is 24 REs or 1 CCE.

It should be noted that a given control channel information size mayrepresent different control channel formats, e.g., control channelinformation of Size 1 may, for example, correspond to a non-MIMOdownlink allocation, and an uplink non-MIMO or uplink multi-user MIMOallocation and control channel information of Size 4 may correspond toan downlink single-user MIMO allocation with 1 code word and to adownlink multi-user MIMO allocation. The code rate may be calculated by:

$\begin{matrix}{{{coding}\mspace{14mu}{rate}} = \frac{{control}\mspace{14mu}{channel}\mspace{14mu}{information}\mspace{14mu}{bits}}{{coded}\mspace{14mu}{control}\mspace{14mu}{channel}\mspace{14mu}{bits}}} \\{= \frac{{control}\mspace{14mu}{channel}\mspace{14mu}{information}\mspace{14mu}{bits}}{{number}\mspace{14mu}{of}\mspace{14mu}{{REs} \cdot {bits}}\mspace{14mu}{per}\mspace{14mu}{RE}}}\end{matrix}$I.e., for example, the coding rate for control channel information (CCI)format Size 2 using 4 CCEs (according to Table 3, i.e., 36 REs per CCEand QPSK modulation) is calculated as follows:

$\begin{matrix}{{{coding}\mspace{14mu}{{rate}\left( {{{Size}\mspace{14mu} 2},{4\mspace{14mu}{CCEs}}} \right)}} = \frac{38}{144\mspace{14mu}{{REs} \cdot 2}\mspace{14mu}{{bits}/{RE}}}} \\{= 0.13}\end{matrix}$

In both tables below, it is assumed for exemplary purposes that QPSKcode rates smaller than, e.g., 0.10 are not required, since a code rateof 0.10 is, e.g., sufficient to reach cell edge UEs. Similarly, coderates larger than, e.g., 0.80 are not required since, e.g., the decodingperformance (achievable BLER) is not reasonable due to a decoding errorfloor). Hence, the hatched cells in the tables indicate that the controlchannel information size is not mapped onto the respective coded controlchannel size.

TABLE 3

TABLE 4

Similar to Tables 3 and 4 above, also Table 5 below assumes forexemplary purposes a QPSK modulation of the control channel informationCCI. In contrast to Tables 3 and 4 above, Table 5 exemplifies asituation where different control channel formats (see column “Format”)are used and some of the available formats carry the same number ofcontrol channel information bits, i.e., have the same control channelinformation size. Similar to the example with respect to Tables 3 and 4above, it may be assumed that coding rates below or above a giventhreshold are not used. Furthermore, as can, for example, be seen in therows (Size 2, Format 3), (Size 4, Format 6) or (Size 4, Format 7) themapping to certain CCE aggregation sizes may be inhibited. For example,such restriction of the mapping to only a subset of the available CCEaggregation sizes may be feasible, if for example, only specific codingrates for transmitting the control channel information of the givenformat are needed to ensure the desired reliability of the transmission,e.g., due to having to meet a given BLER for cell edge UEs (limitationon lower code rates) or to avoid a decoding error floor (limitation onhigher code rates). Considering the combination (Size 5, Format 8), thecontrol data on the control channel may, for example, need a highprotection level, so that only coding rate 0.15 is used, i.e., the CCIof the control channel format is always mapped to 8 CCEs.

TABLE 5

The limitation of the allowed CCE aggregation sizes for given formatsmay further help to reduce the number of blind detections required by aUE. E.g., if a UE needs to decode format 7 (and not formats 5 and 6), ithas to perform blind decodings only on 2 CCE aggregation sizes (4, 2CCEs) instead on all CCE aggregation sizes. If an UE needs to decodeformats 6 and 7 (and not format 5), it still needs to perform blinddecodings on 4 and 2 CCEs. If a UE needs to decode formats 5, 6 and 7,it would require blind decodings of 8, 4 and 2 CCEs.

As will be discussed below in further detail, the control channelinformation of the respective control channel format formats mayoptionally include an identifier to allow the receiving entitydistinguishing the different formats.

In one exemplary embodiment, the different control channel formats aredefined as in 3GPP Tdoc. R1-074906, “PDCCH payload formats, sizes andCCE aggregation,” 3GPP TSG-RAN WG1 Meeting #51, November 2007 (availableat http://www.3gpp.org and incorporated herein by reference):

-   -   Format 1: Uplink assignment (UL)    -   Format 2: Downlink non-MIMO assignment (compact DL assignment)        (DL-C)    -   Format 3: Single-user MIMO downlink assignment (1 code word)        (DL-SU1)    -   Format 4: Single-user MIMO downlink assignment (2 code words)        (DL-SU2)    -   Format 5: Multi-user-user MIMO downlink assignment (DL-MU)    -   Format 6: Beamformed or open loop transmit diversity downlink        assignment (DL-BF/OLT)

In this exemplary embodiment, the following mechanisms may be applied:

-   -   The MIMO formats (Formats 3, 4 and 5) may preferably be applied        to mobile stations (UEs) in high geometry (close to the cell        center/experiencing only little interference), which means that        those formats should be preferably transmitted with higher code        rates, i.e., transmission with low code rates is not required    -   The non-MIMO format and the UL format (Formats 1 and 2) may be        applied to all UEs in the system, e.g., needed for cell-edge        coverage and needed for cell-center UEs without MIMO        transmission, i.e., these formats may be transmitted with a wide        range of code rates.    -   Format 6 may not or may rarely be needed for cell-center UEs and        may, hence, be transmitted preferably with low code rates.

Depending on the control channel information size of the respectiveformat this will result in different CCE aggregation sizes. An exampleof the mapping of the respective control channel information sizes andformats is shown in Table 6 below (even though the Format SU2 should betransmitted mapped onto high code rates, there may be limitation inmaximum reasonable code rate—as mentioned earlier—due to error floorissues):

TABLE 6

When dealing with different control channel formats having the samecontrol channel information size, it may be thus advantageous to allowfor two or more different numbers of coded control channel informationand/or modulation symbols (CCEs) for a respective control channelinformation format associated to modulation and coding schemes ofdifferent spectral efficiency so that also the geometry of the user maybe taken into account.

The selection of the number of coded control channel information and/ormodulation symbols to which the control channel information of a formatis to be mapped may, for example, be additionally or alternatively basedon other parameters such as received signal strength of the controlchannels, fading or frequency selectivity of the downlink channel, theavailable transmit power or simply the receiver type.

Generally, it should be noted that the control channels may, forexample, comprise scheduling related control information, i.e., thecontrol channel may also be referred to as scheduling related controlchannels. In some exemplary embodiments of the invention the controlchannels are L1/L2 control channels for providing the users (mobilestations) with L1/L2 control information related to uplink and/ordownlink data transmissions on a shared channel. In some exemplaryembodiments, each control channel comprises the L1/L2 control channelinformation related to uplink and/or downlink data transmission on ashared channel to/from a single user/mobile station. Alternatively or inaddition thereto, a control channel may optionally also carry pagingrelated information or information related to a response to an uplink(random) access procedure.

FIG. 8 shows an exemplary structure of the processing of control channelinformation of plural control channels on the physical layer accordingto an embodiment of the invention. For illustrative purposes only, theprocessing of two control channels is shown (of course, in real-lifesystems there may be typically more than two control channels providedin a subframe). Further, not shown in FIG. 8, there may be a ratematching unit between the coding section and the modulator for adaptingthe coding rate of the coding section to a desired coding rate (e.g, bypuncturing or repetition).

Each of the control channel information has a certain format (orstructure), i.e., the control information may comprise different fieldsand parameters. In one embodiment, the control information may have theformats as shown in FIG. 14, FIG. 15 and Table 14 or as in Table 1 andTable 2 in the Technical Background section. Due to the differentformats, it may be also assumed that each of the formats of the controlchannel information has a different size in terms of the number of bits.

Another embodiment of the invention considers the design of acommunication scheme for control channels for the system bandwidthagnostic design for LTE. This system bandwidth design is exemplarilyshown in Table 7 below (see also 3GPP Tdoc. R1-074906 mentionedpreviously herein):

TABLE 7 BW 1.4 MHz 1.6 MHz 3 MHz 3.2 MHz 5 MHz 10 MHz 15 MHz 20 MHz 22MHz RBs 6 7 15 16 25 50 75 100 110 Payload UL UL Size 1 DL- DL- [35 bit]BF/OLT BF/OLT DL-SU1 Payload DL-SU1 UL UL UL Size 2 DL- DL- DL-C [39bit] BF/OLT BF/OLT DL-SU1 Payload DL-MU DL-MU DL-SU1 DL- UL UL UL ULSize 3 DL-SU2 DL-SU2 BF/OLT DL-C DL-C DL-C DL-C [43 bit] Payload DL-MUDL-MU DL-SU1 DL- DL- Size 4 DL-SU2 DL-SU2 DL-MU BF/OLT BF/OLT [49 bit]DL-SU1 Payload DL-SU2 DL-MU DL-SU1 DL- Size 5 DL-SU2 DL-MU BF/OLT [56bit] DL-SU2 Payload DL- DL- Size 6 SU1 BF/OLT [65 bit] DL-MU DL- DL- SU1SU2 DL- MU DL- SU2

As can be seen from Table 7 a given format (e.g., Format DL-C) hasdifferent control channel information sizes, depending on the systembandwidth. This is caused by the Resource Block (RB) allocation fieldbeing system bandwidth dependent, which causes that different formats,e.g., Format UL (or Format DL-C) and Format DL-SU2, having differentsizes for the same system bandwidth, to have the same control channelinformation size for different system bandwidths. E.g., for systembandwidths of 10 MHz (50 RBs) and larger, the Format UL (or Format DL-C)is mapped on control channel information size (payload) size 3. The samesize is used for Format DL-SU2 (and also Format DL-MU) for systembandwidths of 1.4 and 1.6 MHz.

Similarly, the Format DL-SU2 (and also Format DL-MU) for systembandwidths of 3.0 and 3.2 MHz is mapped on payload size 4, which is alsoused for the Format DL-BF/OLT for system bandwidths of 10 and 15 MHz.

Additionally, the Format DL-SU2 for system bandwidths of 5 to 15 MHz ismapped on payload size 5, which is also used for the Format DL-BF/OLTfor a system bandwidth of 20 MHz.

Applying the principles introduced in Tables 5 and 6 (formats beingmapped on the same size being mapped on different CCE aggregation sizes)across different system bandwidths, e.g., a mapping as shown in Table 8below, may be defined.

TABLE 8

In another embodiment of the invention, the size of the CCEs may dependon the system bandwidth, where the size typically increases withincreasing system bandwidth.

Examples are shown in Tables 9 and 10. Applying the CCE numerology fromTable 9 to the formats and CCE aggregation sizes from Table 8 will yielddifferent code rates as shown in Table 11. As can, for example, be seenfor the DL-SU2 format, the same CCE aggregation sizes (2 and 4) are usedfor this format in all system bandwidths. This feature may simplify thebase station and UE operation in that the blind detection of the controlchannel format is simplified due to the limited number of CCEaggregations sizes to which the format may be mapped.

TABLE 9 BW 1.4 MHz 1.6 MHz 3 MHz 3.2 MHz 5 MHz 10 MHz 15 MHz 20 MHz 22MHz RBs 6 7 15 16 25 50 75 100 110 CCE size 24 24 24 24 24 36 36 36 36[REs]

TABLE 10 BW 1.4 MHz 1.6 MHz 3 MHz 3.2 MHz 5 MHz 10 MHz 15 MHz 20 MHz 22MHz RBs 6 7 15 16 25 50 75 100 110 CCE size 16 16 20 20 24 36 36 48 48[REs]

TABLE 11

Table 12 provides another example applying the CCE numerology from Table10 to the formats and CCE aggregation sizes from Table 8.

TABLE 12

Concerning the processing of the control channel information at thetransmitting entity, the control channel information of a respectivecontrol channel is first subject to coding and modulation by means of acoder and a modulator. The coder codes the control channel informationat a given coding rate (e.g., in the range of 0.1 to 1). Differentcoding rates might, e.g., be generated by puncturing and repetition ofthe output bits of a coder with a given mother code rate. The coded bits(also referred to as coded control channel information herein) are thensubjected to modulation on a modulator. The modulator receives groups ofcoded bits (so-called codewords) or forms the codewords out of the inputcoded bits, Each codeword is then mapped by the modulator to amodulation symbol. The number of coded bits of a codeword therebydepends on the modulation scheme level (for an M-bit codeword amodulation scheme with 2^(M) distinct modulation symbols is needed). Forexample, the modulator may use a modulation scheme such as BPSK, QPSK,16QAM, 64QAM or the like. The modulator outputs modulation symbols. Forexample, the modulation symbols are characterized by inphase andquadrature component in the I- and Q-plane.

As explained previously, each control channel information format may beassociated to at least one modulation and coding scheme. A modulationand coding scheme typically comprises a coding rate to be employed bythe coder and a modulation scheme to be applied by the modulator. Themodulation and coding scheme(s) associated to the respective controlchannel information formats is chosen so as to align the size of thecontrol channel information of different formats to an equal number (orequal numbers) of coded control channel information bits and/ormodulation symbols for each control channel.

Hence, in this example, the modulators modulating the coded bits of thetwo control channels output an equal number of modulation symbols. Themodulation symbols may next be multiplexed by a multiplexer and aresubsequently processed by an OFDM modulation section that outputs OFDMsymbols. These OFDM symbols carry the information of the controlchannels and are subsequently mapped to the physical channel resources,e.g., as shown in FIG. 4, for transmission.

At the receiver side (here, at the mobile stations) a respective one ofthe OFDM symbols is demapped from the physical channel resources at atime instance and is provided to an OFDM demodulation section thatdemodulates the OFDM symbols to obtain a set of modulation symbols. Thedemultiplexer demultiplexes the modulation symbols and thereby tries torecover the individual control channels. The demultiplexed modulationsymbols of a respective control channel are then provided to ademodulator that demodulated the symbols to generate a series ofcodewords. These codewords are then provided to a decoder that tries torecover the control channel information of the respective controlchannel.

In this exemplary embodiment, it is assumed that the modulation andcoding scheme for the control channels is not known to the receivingentities (except for the receiving entities being aware of theassociation between modulation and coding schemes and the respectivecontrol channel formats, but not of the actual control channelinformation formats on the channels). Hence, a receiving entity mayperform a blind detection of the modulation and coding scheme of thecontrol channels. Generally it should be noted that according to anembodiment of the invention that certain parameters used for OFDMdemodulation, demultiplexing, demodulation and decoding may be known tothe receiving entities, for example by means of (pre-)configuration;however, not all parameters necessary to revert the physical layerprocessing are available so that in some steps of the physical channelprocessing the receiver have to find out the appropriate parameters intrial-and-error fashion, i.e., blind detection.

One example for blind detection is that the receiver (mobile station)demodulates the received signal and tries to decode the control channelsusing one of the different modulation and coding schemes that have beendefined for the control channel information formats. A mechanism forblind detection for use in one embodiment of the invention is similar tothat specified in sections 4.3.1 and Annex A in 3GPP TR 25.212:“Multiplexing and channel coding (FDD),” Release 7, v. 7.1.0, June 2006and in 3GPP TSG-RAN WG1 #44 R1-060450, “Further details on HS-SCCH-lessoperation for VoIP traffic,” February 2006 or 3GPP TSG-RAN WG1 #44bisR1-060944 “Further Evaluation of HS-SCCH-less operation,” March 2006(all three documents available at http://www.3gpp.org and beingincorporated herein by reference).

FIG. 9 shows another exemplary structure of the processing of controlchannel information of plural control channels on the physical layeraccording to an embodiment of the invention. Essentially, the sameprocessing steps as in FIG. 8 are provided for the control channels.

The control channel information of the respective control channels areindividually encoded by means of a coder (coding section) first. Similarto FIG. 8, there may be a rate matching unit between the coding sectionand the modulator for adapting the coding rate of the coding section toa desired coding rate (e.g., by puncturing or repetition). In contrastto the physical layer processing in FIG. 8, the coded bits of thechannels output by the coding are multiplexed in this embodiment and themultiplexed coded bits of the control channel are subjected tomodulation in a modulation section. Hence, in this exemplary embodiment,the modulation scheme for all control channels is the same. Accordingly,in order to align the align the size of the control channel informationof different formats, the coding rate of the modulation and codingscheme associated to a respective control channel has to be selected sothat the coding section outputs an equal number of coded control channelinformation for each of the control channels. (Due to the use of thesame modulation scheme for all control channels in this example, themodulation of the coded bits of each control channel will thus result inan equal number of modulation symbols/resource elements for each controlchannel as well.)

The modulation symbols for the control channels output by the modulationsection are then subject to OFDM modulation and physical channel mappingas explained previously with respect to FIG. 8. Accordingly, the reverseprocessing on the receiver side is similar to the one explained for FIG.8 except for the demodulation of the symbols will provide a streamcomprising codewords of all control channels, which has to bedemultiplexed so as to obtain the codewords of the respective controlchannels. The codewords of the respective control channels aresubsequently tried to be decoded to recover the control channelinformation of the respective control channels.

Alternatively, multiplexing at the transmitter may also be performedafter modulation. Accordingly, also the receiver must be adaptedaccordingly to perform demultiplexing prior to decoding. Furthermore, inanother embodiment of the invention, additional steps may be performedat the transmitter prior to the physical channel mapping, such asscrambling, interleaving, etc. Similar measures to revert the effect ofthe respective steps are to be foreseen at the receiver accordingly.Moreover, in case the control channels are mapped onto CCEs, there maybe additional steps related to the CCE mapping and multiplexing at thetransmitter, and respective steps (demultiplexing and demapping) at thereceiver.

FIG. 10 shows, in accordance with an exemplary embodiment of theinvention, the use of two different modulation and coding schemes havinga common modulation scheme for aligning the number of coded controlinformation bits of the control channel information of control channels,where the control channel information have different formats. In thisexample, two different control channel information formats, format 1 andformat 2, with different sizes, are considered for exemplary purposes.Control channel format 1 of a first control channel is assumed to have asize of 12 bits, while control channel format 2 of a second controlchannel is assumed to have a size of 18 bits. (It should be noted thatit may be derived from Table 1 and Table 2 above and from Table 3 aswell as FIG. 14 and FIG. 15 that typically the control channelinformation formats will have more than this rather small number of bitsin real-life implementation and that the embodiments described withrespect to FIG. 10 to FIG. 13 should be understood as to illustrate theconcept). The size of the two different control channel informationformats should be aligned in this example. Each of the two formats isassociated to a modulation and coding scheme for this purpose. Format 1is associated to a modulation and coding scheme {coding rate: 1/3;modulation scheme: 16QAM} and Format 2 is associated to a modulation andcoding scheme {coding rate: 1/3: modulation scheme: 16QAM}. Accordingly,the modulation scheme of the control channels may, for example, bepreconfigured in this example. Hence, in order to align the size of thecontrol channel information, the coding rate of the respectivemodulation and coding schemes for format 1 and format 2 have beenselected so that an equal number of coded bits is obtained by coding.The 12 bits of format 1 are coded at a code rate of 1/3 resulting in a36 coded bits. Similarly, the 18 bits of format 2 are coded at a coderate of 1/2 so that also 36 coded bits are obtained.

As a 16QAM modulation is used, codewords of 4 bits are mapped to asingle modulation symbol by modulation. Hence, when modulating the 36coded bits of the respective control channels 9, modulation symbols areobtained for each control channel in this example. It should be notedthat there may be of course more than two control channels provided fortransmission at a given time instance and that there may also be morethan two formats of the control channel information provided.Accordingly, a modulation and coding scheme for each format of thecontrol channel information (given that the formats differ in size)should be provided.

In a further embodiment of the invention, at least two control channelinformation formats out of the possible control channel informationformats have the same size. Accordingly, to map these at least twocontrol channel information to a an equal number of coded bits ormodulation symbols, it has to be taken care that the modulation andcoding schemes for these equal-sized format differ from each other.

If however one parameter of the modulation scheme is to be used for allformats (for example, a common modulation scheme is to be used for allcontrol channels irrespective of the format), this will yield the samemodulation and coding scheme for these control channel informationformats of equal size. Hence, to be still able to identify the correctcontrol channel format, in another embodiment, the receivers may decodethe control channel information and may compare the resulting controlchannel information against the equal-sized formats to identify thecorrect format. Alternatively, in another embodiment, it may beadvantageous to include a format identifier (e.g., control channelinformation format field) to the control channel information or to thecoded bits (by the coder) so as to uniquely identify the control channelinformation format. It should be noted that a control channel formatidentifier may be also used by default, i.e., irrespective of whetherthere exist control channel formats of equal size or not or of whetherthe control channel information formats are mapped to different numbersof coded bits or modulation symbols.

If all control channel information formats have a different size (interms of number of bits) the modulation and coding schemes for therespective formats will all be different, so that no identifier would beneeded.

Additionally, selected control channel information formats may have thesame size, however, a given mobile station may not need to decode allformats. Instead, the mobile station may only use a single one. In thiscase, a format identifier is not required. This could, for example, berealized by pre-configuring a mobile station (UE) to receive onlycontrol channels for downlink single-user MIMO mode. Accordingly, themobile station does not need to decode other formats, e.g., for non-MIMOor for multi-user MIMO. Thus, even if the size of the formats would beidentical, the mobile station needs to know only how to interpret thecontent of the control channel without a format identifier beingrequired in this case.

Alternatively, if different control channel information formats have thesame size, they may be mapped on exclusive CCE aggregation sizes. Inthis case the format identifier may also not be required, since theformat is known from the CCE aggregation size. This is exemplarily shownin Table 13.

TABLE 13

Alternatively or additionally, in another embodiment of the inventionthe different control channel formats may also be distinguished byapplying different interleaving schemes and/or scrambling to the controlchannel information, depending on the respective format of the controlchannel. For example, the different control channel formats may be eachassociated to different interleaving schemes for the control channelinformation data. Optionally, there is a unique mapping between acontrol channel format and a corresponding interleaving scheme, i.e.,the control channel formats may be associated to mutually distinctinterleaving schemes.

Similarly, the different scrambling codes may, for example, be appliedto the control channel information, wherein the applicable scramblingcode is chosen based on the control channel format of the controlchannel information. Optionally, a unique mapping between a controlchannel format and a corresponding scrambling code may be provided,i.e., the control channel formats may be associated to mutually distinctscrambling codes.

It should be noted that the selected interleaving scheme or scramblingcode may additionally depend on other parameters, such as, e.g., the CCEaggregation size, the cell identifier (cell ID) of the radio cell themobile station (UE) is located in and/or the identifier of the mobilestation (UE ID).

Further it should be noted that according to one exemplary embodiment ofthe invention the different interleaving schemes are obtained using thesame interleaving algorithm but initiating the algorithm with differentinitialization parameter values.

In a similar fashion, the different scrambling codes may, for example,be generated by using a common algorithm for generating scrambling codesand initializing this algorithm with different initialization parametervalues depending on the control channel format.

FIG. 11 shows, in accordance with an exemplary embodiment of theinvention, the use of two different modulation and coding schemes foraligning the number of modulation symbols of the control channelinformation of control channels, where the control channel informationhave different formats and sizes. In this exemplary embodiment, themodulation scheme for the different formats is not predefined.Accordingly, it is not necessary (but is still possible) that the numberof coded bits for the different formats is matched.

In this exemplary embodiment, again, two different control channelformats, format 1 and format 2, are considered for exemplary purposes.Control channel format 1 is associated to a modulation and coding scheme{coding rate: 1/3; modulation scheme: 16QAM}, while control channelinformation format 2 is associated to a modulation scheme {coding rate:1/2; modulation scheme: QPSK}.

Accordingly, the 12 bits for format 1 are first coded at rate 1/2resulting in 36 coded bits. These coded bits are subsequently subjectedto a 16QAM modulation (codeword size: 4 bits) to obtain 9 modulationsymbols. Similarly, the 9 bits of format 2 are encoded at rate 1/2resulting into 18 coded bits. These coded bits are then subjected toQPSK modulation (codeword size: 2 bits) so that also 9 modulationsymbols as for format 1 are obtained.

FIG. 10 and FIG. 11 thus exemplarily illustrate the coding andmodulation step in the physical layer processing of the control channelsas, for example, shown in FIG. 8. While in the example of FIG. 10 thenumber of coded bits is matched to a single number of coded bits for allcontrol channel formats, FIG. 11 illustrates an example where the numberof modulation symbols for all control channel information formats ismatched.

As indicated above, another aspect of the invention is related to a moreflexible control channel configuration which may still facilitate blinddetection of the control channels on the downlink physical resourceswithout implying a high level of complexity for the receiving entities.

FIG. 12 shows, in accordance with an exemplary embodiment of theinvention, the use of different modulation and coding schemes foraligning the number of modulation symbols of the control channelinformation of control channels to two numbers of modulation symbols,where the control channel information have different formats. In thisexemplary embodiment, three different control channel informationformats of different size are assumed for exemplary purposes. Controlchannel information format 1 is assumed to have a size of 12 bits and isassociated to a modulation and coding scheme {coding rate: 1/3;modulation scheme: 16QAM}. Control channel information format 2 isassumed to have a size of 9 bits and is associated to a modulation andcoding scheme {coding rate: 1/2; modulation scheme: QPSK}. Controlchannel information format 3 is assumed to have a size of 18 bits and isassociated to a modulation and coding scheme {coding rate: 1/2;modulation scheme: QPSK}. Hence, format 2 and format 3 are associated tothe same modulation and coding scheme, but the resulting number ofmodulation symbols will be different due to the different sizes of thetwo formats.

When applying the modulation and coding scheme of format 1 and format 2to the respective control channel information, 9 modulation symbols willbe obtained for both control channel information format 1 and 2. Forcontrol channel information format 3, the coding of its 18 bits at coderate 1/2 will result in 36 coded bits and the subsequent QPSK modulationwill generate 18 modulation symbols. Hence, in this exemplaryembodiment, applying a the modulation and coding scheme associated tothe different control channel information formats to the control channelinformation of the control channels will generate either 9 modulationsymbols or 18 modulation symbols.

As explained above, there may be various reasons to generate twodifferent numbers of modulation symbols (or coded bits) for differentcontrol channel formats. One reason may be that in order to generate 9modulation symbols for format 3, a modulation scheme of high spectralefficiency would be needed (for example, {coding rate: 1/2; modulationscheme: 16QAM}). However, this modulation and coding scheme may be toounreliable for transporting of the control channel information (e.g, dueto the channel conditions) or may be a modulation and coding schemesimply not allowed for use with control signaling, so that same may notbe used. Hence, a second number of coded bits or modulation symbols towhich the control channel information may be matched may be defined.

Though in FIG. 12 the different control channel information formats maybe considered to be assigned one modulation and coding scheme, inanother embodiment, the different control channel information formatsmay be assigned to two (or even more) modulation and coding schemes sothat selectively different but given/known numbers of coded bits ormodulation symbols may be generated for all control channel informationformats. For example, there may be three numbers of modulation symbolsdefined in the system, denoted M₁, M₂ and M₃. Accordingly, the differentcontrol channel information formats may be assigned to at least one andat maximum to three different modulation and coding schemes for mappingthe control channel information of a respective format to either one ofor a combination of M₁, M₂ and M₃ modulation symbols. For example,format 1 may be associated to two modulation and coding schemes mappingthe control information of that format to either M₁ or M₂ modulationsymbols, format 2 may be associated to three modulation and codingschemes mapping the control information of that format to either M₁, M₂or M₃ modulation symbols and format 3 could be associated to twomodulation and coding schemes mapping the control information of thatformat to either M₂ or M₃ modulation symbols. In one embodiment, thenumbers M₁, M₂ and M₃ are selected such that (assuming that M₁ is thesmallest number) M₂=n×M₁ and M₃=m×M₁ (n and m being different positiveinteger numbers). A CCE may be defined as a set of M₁ modulation symbolsand, hence, aggregating n (m) CCEs would yield M₂ (M₃) modulationsymbols, Alternatively, the size of a CCE may be defined such that M₁modulation symbols define k CCEs, then aggregating k×n (k×m) CCEs wouldyield M₂ (M₃) modulation symbols.

This flexible definition of different number of coded bits or modulationsymbols to which the different control channel information formats maybe matched may allow for using adaptive modulation and coding for thecontrol channels so as to, for example, react to changing channelconditions, as will be explained with respect to FIG. 13 next. FIG. 13shows, in accordance with an exemplary embodiment of the invention, theuse of different modulation and coding schemes for aligning the numberof modulation symbols of the control channel information of a controlchannel to two numbers of modulation symbols (CCEs), where the controlchannel information have different formats. The decision on whether tomap the control channel information to a first number of modulationsymbols or a second number of modulation symbols may, for example, bebased on the channel quality or geometry of the user for which thecontrol channel information is sent, as mentioned previously. Anotherparameter for such a decision may also be the format of the controlchannel information, which is mapped onto a given control channelinformation size. For example, in this embodiment of the invention, two(or more) modulation schemes may be defined for a control channelformat. Depending on the channel quality of the downlink physicalchannel transporting the control channels, one of the modulation andcoding schemes for the formats may be selected respective. For example,if the channel quality is below a certain threshold value, a modulationand coding scheme may be used for the control channel information of agiven format that is providing a spectral efficiency/data rate lowerthan a second modulation and coding scheme for the control channelinformation of a given format that is to be applied, if the channelquality is above or equal a threshold level. In another embodiment ofthe invention, adaptive modulation and coding as well as power controlmay be applied to the L1/L2 control channels, i.e., the L1/L2 controlsignaling to a mobile station close to the cell center (highgeometry/SINR) might be transmitted with low power and/or a high MCSlevel (smaller number of modulation symbols or CCEs), whereas the L1/L2control signaling to an MS close to the cell edge (low geometry/SINR)might be transmitted with high power and/or a low MCS level (largernumber of modulation symbols or CCEs).

Accordingly, if more than two modulation and coding schemes, i.e., Nmodulation and coding schemes, are defined for a respective format,there may be N-1 thresholds defined to distinguish the different channelquality level ranges in which the different modulation and codingschemes are to be used. It may be further advantageous, if themodulation and coding scheme level is selected directly proportional tothe channel quality, i.e., a lower level modulation and coding scheme(i.e., offering a lower data rate/spectral efficiency) for a poorchannel quality and a higher level modulation and coding scheme (i.e.,offering a higher data rate/spectral efficiency) for a better channelquality.

FIG. 14 shows several different formats of control channel informationand their mapping to a single codeblock size by means of modulation andcoding according to an exemplary embodiment of the invention. In FIG. 14six different exemplary formats of control channel information areshown. Generally, it should be understood that part of the controlchannel information may be considered a pointer to the location of adata block comprising user data for an individual user within the datapart of a sub-frame (or a number of consecutive sub-frames). In otherwords, the control data may indicate to a user whether and, ifapplicable, which resource block(s) are assigned to the mobile station(user), which transport format (link adaptation) is used fortransmitting the user data destined to the mobile station, etc.

According to some embodiments of the invention, the structure or formatof the information carried by the control channels may be separated intothe categories shared control information (SCI) and dedicated controlinformation (DCI).

The SC1 part of the control signaling may contain information related tothe resource allocation (also referred to as Cat. 1 information). TheSCI part may comprise the user identity (UE ID field) indicating theuser (or the group of users) being allocated a resource, RB allocationinformation, indicating the resources (resource block(s)) allocated tothe user. The resource allocation field may indicate the resourceblock(s) that have been allocated for uplink user data transmission onan uplink data channel or, alternatively, the resource block(s) that areto be used for downlink user data transmission to the respective mobilestation or group of mobile stations identified by the UE ID field on ashared downlink channel (e.g., the Downlink Shared CHannel (DSCH) forSAE/LTE systems). The number of resource blocks on which a user isallocated can be dynamic. Optionally the SCI may further include anindication of the duration of assignment, if an assignment over multiplesub-frames (or TTIs) is possible in the system.

The DCI part of the control signaling may contain information related tothe transmission format (also referred to as Cat. 2 information) of thedata transmitted to a scheduled user indicated by Cat. 1 information.Moreover, in case of application of (Hybrid) ARQ, the DCI may also carryretransmission protocol related information (also referred to as Cat. 3information) such as (H)ARQ information. The DCI needs only to bedecoded by the user(s) scheduled according to the Cat. 1 information.

The Cat. 2 information within the DCI may, for example, compriseinformation on at least one of the modulation scheme, thetransport-block (payload) size (or coding rate), MIMO relatedinformation, etc. The Cat. 3 information may comprise HARQ relatedinformation, e.g., hybrid ARQ process number, redundancy version,retransmission sequence number. It should be noted that either thetransport-block size (payload size) or the code rate can be signaled inthe Cat. 2 information. In any case payload size and code rate can becalculated from each other by using the modulation scheme informationand the resource information (number of allocated resource blocks).

In case a MIMO scheme is used or is to be used for the user datatransmission, several information elements in the control channelinformation may need to be provided for each of the MIMO streams.Accordingly, some of the information elements may be provided severaltimes in the exemplary L1/L2 control information, e.g., for each MIMOstream. Further, it may also be possible that some of the differentparameters (such as payload size, modulation scheme, etc.) are to beused by all or a subset of the MIMO streams.

The first exemplary format shown in FIG. 14 is a simple control channelinformation format, which may be used on control channels for usersutilizing no specific MIMO scheme (e.g., SISO—Single Input SingleOutput, or simple transmit and/or receive diversity schemes, which donot require additional antenna related information). This format may,for example, only comprise RB allocation information, an identificationof the user(s) for which the control information is intended (e.g., bymeans of the UE ID field or by an implicit identification such as a UEspecific CRC), the payload size (respectively transport format—asexplained above), the modulation scheme and HARQ information.

The second exemplary format may, for example, be used for user datatransmissions to employ a MIMO scheme. Similar to the first format shownin FIG. 14, also this format comprises RB allocation information, anidentification of the user(s) for which the control information isintended, the payload size (respectively transport format), themodulation scheme and HARQ information. Further, the format may includeadditional information elements indicating the number of MIMO streamsand precoding information (e.g., number of MIMO streams and a precodingvector or an index value pointing to a preconfigured precoding vector).As only one “set” of information elements relating to payload size,modulation scheme and HARQ information, this may mean that all streamsindicated in the number of streams field use the same payload size andmodulation scheme and that all streams may be handled by a single HARQprocess. Alternatively, the payload size, modulation scheme, etc. onlyconfigure a subset (e.g., one) of the multiple streams and informationon additional streams is transmitted separately.

The third control channel information format shown in FIG. 14 comprisesthe same information elements as the second example, except for theassumption that more precoding related information are included in thecontrol information (e.g., larger precoding vector, e.g., indexreflecting a larger index space).

The next, fourth example of a control channel information format alsorelates to the use of a 2-stream MIMO scheme. In this example, thedifferent payload sizes are used for the respective MIMO streams, sothose two payload size fields are included in the format. Similar to theprevious examples, the same modulation scheme may be used for both MIMOstreams and the streams may be handled by a single HARQ process.Alternatively, the modulation and HARQ information may configure asingle stream and information on the second stream is transmittedseparately, e.g., on another control channel.

The fifth exemplary format in FIG. 14 is essentially similar to thefourth example, except for the use of two separate HARQ processes forthe respective streams of the MIMO scheme. Similarly, the sixthexemplary L1/L2 control information format shown in FIG. 14 assumes twodifferent payload sizes and modulation schemes for the two MIMO streams,while both streams are handled by a single HARQ process.

In general the control channel information may contain partial or fullinformation for multiple MIMO streams for various MIMO configurations.

As can be recognized from the exemplary control channel informationshown in FIG. 14, the format of the control information on the controlchannels may vary depending on the configuration used for user datatransmission. Accordingly, the different formats may not only differ intheir content, i.e., the information elements contained in therespective format and/or the size (in terms of number of bits) of theformats. The control channel information format may, for example, dependon at least one of the following parameters:

-   -   the control channel's relation to a MIMO scheme or beamforming        scheme utilized or to be utilized for the transmission of user        data,    -   the control channel's relation to uplink or downlink        transmission of user data,    -   the control channel's relation to a utilization of localized        mode or distributed mode OFDM transmission for the transmission        of user data.

It should be noted that the examples shown in FIGS. 14 and 15 areintended to exemplarily visualize on an abstract level that there may bevarious different control channel formats resulting in different controlchannel information sizes. There may be additional fields defined forcertain formats (e.g., power control commands for different channels,multi-user MIMO related information, format identifiers, etc.), whichare not shown.

Moreover, some fields may be omitted, since their information can bederived from other fields (e.g., because the fields are merged intoother fields or because related information is signaled on a differentchannel or is pre-configured). Some examples on how individualparameters of the control channel information may be derived from eachother are exemplarily listed below:

-   -   The modulation scheme information may be derived from the        payload size and the RB allocation info    -   The HARQ information may not be required for certain control        channel formats    -   The number of MIMO streams may be derived from some other        control channel fields and/or may be pre-configured

In addition, certain fields of the control channel information may havedifferent sizes in different control channel formats, e.g.:

-   -   The RB allocation information field may be smaller for the first        format in order to keep this control channel format as small as        possible (to improve coverage, as a small format size yields a        lower coding rate/higher coding gain). This may, however, cause        some restrictions in the flexibility of the RB allocation.    -   For an uplink related control channel, the RB allocation        information field may be smaller than for some downlink related        control channels

Hence, as indicated in FIG. 14, a modulation and coding scheme for therespective control channels may be chosen based on the format of thecontrol information on the respective control channel so as to align thesize of the control channel information on the physical resource.According to another embodiment, the different control channel formatsas shown in FIG. 14 and FIG. 15 may also be mapped to two differentcodeblock sizes (i.e., the number of coded control information bits) asshown in FIG. 15.

The subsequent table shows an exemplary definition and overview of thecontent of the control channels according to an exemplary embodiment ofthe invention. It should be noted that the size of the respective fieldsis only mentioned for exemplary purposes.

TABLE 14 Field Size Comment Cat. 1 ID (UE or group specific) 8 Indicatesthe UE (or group of (Resource UEs) for which the data indication)transmission is intended; the indication may be implicit, e.g., in formof a CRC Resource assignment 6 Indicates which (virtual) resource units(and layers in case of multi- layer transmission) the UE(s) shalldemodulate. Duration of assignment 2 The duration for which theassignment is valid, could also be used to control the TTI or persistentscheduling. Cat. 2 Multi-antenna related 0-20 Content depends on the(transport information MIMO/beamforming schemes format) selected.Modulation scheme 2 QPSK, 16QAM, 64QAM. In case of multi-layertransmission, multiple instances may be required. Payload size 6Interpretation could depend on, e.g., modulation scheme and the numberof assigned resource units (c.f. HSDPA). In case of multi- layertransmission, multiple instances may be required. Cat. 3 If Hybrid ARQ 3Indicates the hybrid ARQ process (HARQ) asynchronous process number thecurrent transmission is hybrid ARQ addressing. is adopted Redundancy 2To support incremental version redundancy. New data 1 To handle softbuffer clearing. indicator If Retransmission 2 Used to derive redundancysynchronous sequence version (to support incremental hybrid ARQ numberredundancy) and ‘new data is adopted indicator’ (to handle soft bufferclearing).

Other embodiments of the invention relate to limiting the number ofblind detection trials so as to further reduce the complexity of thecontrol channel configuration. In order to limit/reduce the number ofblind detection trials to be carried out by the receiver (mobilestation, UE), a receiver may, for example, try to detect only a subsetof possible defined formats and sizes (resources) of the L1/L controlsignaling.

This may require some configuration. An according configuration shouldmainly affect the receiver, but may—in some cases—also affect thetransmitter.

In one exemplary embodiment, the receiver is configured such that ittries to receive a subset of formats and/or a subset of sizes (MCSlevels for certain formats) only. The receiver may be additionally oralternatively configured such that it tries to receive control channelson only some of the physical resources used for control channels.

In one exemplary scenario, a receiver may be preconfigured in a MIMOmode 1 for downlink and therefore only tries to receive the formatdefined for MIMO mode 1. Additionally, this mobile station may only tryto receive a certain codeblock size for this MIMO mode 1 format of thecontrol channel information. Further, the mobile station may also try toreceive this MIMO mode 1 format on only a subset of the control channelresources.

In another exemplary scenario, a mobile station may be active in uplinkand downlink. This mobile station may thus receive uplink relatedcontrol channels on a first subset of the overall control channelresources and may also receive downlink related control channels on asecond subset of the overall control channel resources.

In most cases this operation may imply that the transmitter has limitedflexibility in terms of mapping certain control channel formats oncertain resources only. This can be seen as a transmitter configuration.Generally, the transmitter flexibility may be limited by the receiver(UE) complexity (number of possible blind detection trials).

In one exemplary embodiment of the invention, the configuration of thereceivers is preformed by the network (transmitter). The configurationmay be common information to all receivers that may be broadcast by theaccess network. Alternatively, the configuration may be dedicated to anindividual receiver or a group of receivers. In this alternative,dedicated signaling may be used to transmit the configuration to thereceiver(s). The common configuration may, for example, be transmittedin a broadcast channel and the dedicated information may, for example,be transmitted on a dedicated or shared channel. In some cases, acombination of common and dedicated configuration might be used. E.g., areceiver may be initialized with a baseline common configuration (bybroadcast) and may be reconfigured by dedicated signaling.

Further, the configuration might be carried out dynamically persub-frame. In one exemplary embodiment, a so-called Cat. 0 controlchannel might be configured in the communication system in order toprovide information on the currently transmitted control channelformats, sizes and/or resources. For example, in a given sub-frame, theCat. 0 information may indicate that only control channels related touplink user data transmissions (or alternatively downlink user datatransmission) are transmitted so that only the interested receivers mayneed to receive the control channels. In another example, the Cat. 0information may indicate that the control channels only contain controlchannel information (and thus respective control channel formats) forspecific MIMO modes. In another example, the Cat. 0 control informationmay indicate that control channels are only transmitted on certaincontrol channel resources, or may indicate that control channels conveyonly control channel information of certain sizes.

The Cat. 0 information does not necessarily need to be transmitted everysub-frame. It may also be transmitted on a longer time scale and thecontained information may be valid for a certain time period.

Concerning the embodiments of the invention where multiple codeblocksizes out of a single control channel format may be generated (see, forexample, FIG. 7, FIG. 12, FIG. 13 and FIG. 15) it may be possible toconsider the geornetries/SINR (Signal to Interference-plus-Noise Ratio)state of the mobile stations. For example, mobile stations MS1 and MS2may, for example, be located at the cell edge of a radio cell which isassumed to imply that radio channel quality is lower compared to mobilestations MS3 and MS4, which are supposed to be located near the radiocell center. In order to securely transmit the control signaling, MS1and MS2 are thus assigned more resources on the control channel, i.e., acontrol channel format 1 would be modulated and encoded to generate alarger codeblock (i.e., number of coded control channel information) orlarger number of modulation symbols while MS3 and MS4 having betterchannel quality receive the control signaling with a higher MCS level,i.e., a control channel format 1 would be modulated and encoded togenerate a smaller codeblock (i.e., number of coded control channelinformation) or smaller number of modulation symbols.

In another embodiment of the invention the control signaling (i.e.,control channel information of the control channels) and user data maybe multiplexed. This may, for example, be realized by TDM (Time DivisionMultiplex) as depicted in FIG. 6 and FIG. 7, FDM (Frequency DivisionMultiplex), CDM (Code Division Multiplex) or scattered the timefrequency resources within a sub-frame. Moreover also the differentcontrol channels themselves may be multiplexed in CDM, TDM and/or FDMfashion. In one exemplary embodiment, the multiplexing of user data iscarried out by a combination of TDM and FDM, i.e., the multiplexing maybe performed on a resource element level, whereas control channels aremultiplexed by a combination of CDM and FDM. This exemplary embodimentis illustrated in FIG. 19. On the left-hand side of the figure, aresource grid of a sub-frame of an OFDM channel is shown in which thecontrol channels of the two sets are mapped to the physical resource ina distributed mode. On the right-hand side of the figure a resource gridof a sub-frame of an OFDM channel is shown in which the control channelsof the two sets are mapped to the physical resource in a localized mode.

In the example in FIG. 1 the L1/L2 control information is signaled onseveral L1/L2 control channels. According to one exemplary embodiment,the L1/L2 control channels may be mapped on part of the physicalresource blocks and are equally distributed on all physical resourceblocks. Generally, the mapping of the L1/L2 control channels onto thephysical resource blocks might be done in various ways. For example:

-   -   The control channels may be equally distributed over all        physical resource blocks (as shown in FIG. 1)    -   The control channels may be unequally distributed over all        physical resource blocks    -   The control channels may be (un)equally distributed over        selected physical resource blocks (as, for example, shown in        FIG. 19)

The individual parts of the L1/L2 control information might be encodedin various ways. According to one exemplary embodiment, Cat. 1, Cat. 2and Cat. 3 information is encoded jointly for each mobile station.Another option is to encode Cat. 1 separately from Cat. 2 and Cat. 3information for each mobile station.

Details on the coding and the mapping within a sub-frame of thedifferent categories of L1/L2 control signaling for use in anotherexemplary embodiment of the invention may also be found in 3GPP RAN WG#1Tdoc. R1-061672: “Coding Scheme of L1/L2 Control Channel for E-UTRADownlink,” June 2006 available at http://www.3gpp.org and incorporatedherein by reference.

In some embodiments of the invention, the (L1/L2) control information istransmitted more reliably than the user data, since correct decoding ofthe control information may be a prerequisite to start demodulating anddecoding of the user data. This typically implies that the target blockerror rate for the control signaling should be lower than the targetblock error rate for the user data. In case of employing (hybrid) ARQ,this assumption refers to the target block error rate for the firsttransmission.

Further, it should be noted that the concepts of the invention outlinedin various exemplary embodiments herein may be advantageously used in amobile communication system as exemplified in FIG. 16. The mobilecommunication system may have a “two node architecture” consisting of atleast one Access and Core Gateway (ACGW) and Node Bs. The ACGW mayhandle core network functions, such as routing calls and dataconnections to external networks, and it may also implement some RANfunctions. Thus, the ACGW may be considered as to combine functionsperformed by GGSN and SGSN in today's 3G networks and RAN functions as,for example, radio resource control (RRC), header compression,ciphering/integrity protection and outer ARQ. The Node Bs may handlefunctions as, for example, segmentation/concatenation, scheduling andallocation of resources, multiplexing and physical layer functions. Forexemplary purposes only, the eNodeBs are illustrated to control only oneradio cell. Obviously, using beam-forming antennas and/or othertechniques the eNodeBs may also control several radio cells or logicalradio cells.

In this exemplary network architecture, a shared data channel may beused for communication on uplink and/or downlink on the air interfacebetween mobile stations (UEs) and base stations (eNodeBs). This shareddata channel may have a structure as shown in FIG. 3 or FIG. 4. Thus,the channel may be viewed as a concatenation of the sub-framesexemplarily depicted in FIG. 6 or FIG. 7. According to an exemplaryembodiment of the invention, the shared data channel may be defined asin the Technological Background section herein, as in 3GPP TR 25.814 oras the HS-DSCH as specified in 3GPP TS 25.308: “High Speed DownlinkPacket Access (HSDPA); Overall description; Stage 2,” v. 5.3.0, December2002, available at http://www.3gpp.org and incorporated herein byreference. The shared channel in the downlink may be used to convey thecontrol channels to the individual users (UEs).

Furthermore it should be noted that the different control channelinformation sizes indicated in the various tables herein are onlyexemplary. It should be noted that the exact number of bits of therespective formats as well as the number of formats defined for thecontrol channels may be different to the examples shown in the differenttables and figures herein. Nevertheless, the principles outlined areequally applicable.

Another embodiment of the invention relates to the implementation of theabove described various embodiments using hardware and software. It isrecognized that the various embodiments of the invention may beimplemented or performed using computing devices (processors). Acomputing device or processor may, for example, be general purposeprocessors, digital signal processors (DSP), application specificintegrated circuits (ASIC), field programmable gate arrays (FPGA) orother programmable logic devices, etc. The various embodiments of theinvention may also be performed or embodied by a combination of thesedevices.

Further, the various embodiments of the invention may also beimplemented by means of software modules, which are executed by aprocessor or directly in hardware. Also a combination of softwaremodules and a hardware implementation may be possible. The softwaremodules may be stored on any kind of computer readable storage media,for example, RAM, EPROM, EEPROM, flash memory, registers, hard disks,CD-ROM, DVD, etc.

In the previous paragraphs various embodiments of the invention andvariations thereof have been described. It would be appreciated by aperson skilled in the art that numerous variations and/or modificationsmay be made to the present invention as shown in the specificembodiments without departing from the spirit or scope of the inventionas broadly described.

It should be further noted that most of the embodiments have beenoutlined in relation to a 3GPP-based communication system and theterminology used in the previous sections mainly relates to the 3GPPterminology. However, the terminology and the description of the variousembodiments with respect to 3GPP-based architectures is not intended tolimit the principles and ideas of the inventions to such systems.

Also the detailed explanations given in the Technical Background sectionabove are intended to better understand the mostly 3GPP specificexemplary embodiments described herein and should not be understood aslimiting the invention to the described specific implementations ofprocesses and functions in the mobile communication network.Nevertheless, the improvements proposed herein may be readily applied inthe architectures described in the Technical Background section.Furthermore the concept of the invention may be also readily used in theLTE RAN currently discussed by the 3GPP.

The invention claimed is:
 1. A method performed by a receiving entity,the method comprising the steps of: receiving control information of oneor more of multiple control information formats from a transmittingentity via a physical control channel that is mapped to resourceelements, and performing a detection of the physical control channel onthe resource elements, wherein the physical control channel consists ofa number of coded control information bits, the number being a definedinteger multiple of a smallest number of coded control information bitsthat can be included in one of said multiple control information formatswherein at least two of the multiple control information formats includedifferent numbers of information bits, and wherein the defined integermultiple of the smallest number of coded control information bitscorresponds to an aggregation of multiple modulation symbols or resourceelements.
 2. The method according to claim 1, wherein the detection isperformed on a subset of resource elements on which the controlinformation can be mapped and/or on a subset of the multiple controlinformation formats.
 3. The method according to claim 2, wherein thesubset of the multiple control information formats is configured toindicate a MIMO transmission mode of data transmission.
 4. The methodaccording to claim 1, wherein the detection is performed on a subset ofresource elements that is configured by dedicated control informationand/or common control information that are transmitted from thetransmitting entity.
 5. The method according to claim 1, wherein thedetection is performed on a subset of resource elements that isdynamically configured per sub-frame.
 6. The method according to claim1, wherein the receiving entity is a user equipment (UE).
 7. The methodaccording to claim 1, wherein the transmitting entity is a base station.8. A receiving entity comprising: a receiving unit that receives controlinformation of one or more of multiple control information formats froma transmitting entity via a physical control channel that is mapped toresource elements, and a detection unit that performs a detection of thephysical control channel on the resource elements, wherein the physicalcontrol channel consists of a number of coded control information bits,the number being a defined integer multiple of a smallest number ofcoded control information bits that can be included in one of saidmultiple control information formats wherein at least two of themultiple control information formats include different numbers of codedcontrol information bits, and wherein the defined integer multiple ofthe smallest number of coded control information bits corresponds to anaggregation of multiple modulation symbols or resource elements.
 9. Thereceiving entity according to claim 8, wherein the detection isperformed on a subset of resource elements on which the controlinformation can be mapped and/or on a subset of the multiple controlinformation formats.
 10. The receiving entity according to claim 9,wherein the subset of the multiple control information formats isconfigured based on a MIMO transmission mode.
 11. The receiving entityaccording to claim 8, wherein the detection is performed on a subset ofresource elements that is configured by dedicated control informationand/or common control information that are transmitted from thetransmitting entity.
 12. The receiving entity according to claim 8,wherein the detection is performed on a subset of resource elements thatis dynamically configured per sub-frame.
 13. The receiving entityaccording to claim 8, wherein the receiving entity is a user equipment(UE).
 14. The receiving entity according to claim 8, wherein thetransmitting entity is a base station.